Recent advances in polymer chemistry have lead to the development of novel composition, whose physical and optical characteristics can be altered by exposure to various energy sources such as light. U.S. Pat. No. 6,813,097 discloses the manufacture of optical elements whose optical properties can be manipulated by exposing at least a portion of the element to light, particularly ultraviolet light. The novel materials are particularly useful in the manufacture of intraocular lenses (IOLs) whose optical properties can be manipulated after the IOL has been implanted in a patient.
The materials are prepared by incorporating photopolymerizable macromers into a polymer matrix. Photoinitiators are also incorporated into the matrix. Upon exposure to a specific wave-length of light, the photoinitiator induces the polymerization of the macromers. The polymerization of the macromers causes changes in the physical and optical properties of the optical element, most notable changes in refraction index and/or shape of the material.
In the preferred embodiment, ultraviolet light is used to manipulate the optical properties of the optical element. To prevent premature polymerization of the macromers present, ultraviolet (UV) light absorbers such as benzotriazoles and benzophenones are incorporated in to the optical material. Sufficient UV absorber has been incorporated into the lens that prevents polymerization of the macromers under ambient conditions but allows the use of UV light at relatively safe levels to make the desired adjustments.
While this system has been generally successful, it places limitations on the intensity of the light source used to induce polymerization. This, in turn has been found to limit the rate of polymerization and amount of macromer polymerized, limiting the changes which can be induced in the lens. In addition, the lens still permits some transmission of UV light which, while generally recognized as being within acceptable limits, can potentially cause damage to the interior of the eye.
It would be beneficial to develop a light adjustable optical element whose properties can be adjusted within a range of light intersectors while still offering protection to the users. Specifically, it would be helpful to provide a lens whose properties can be adjusted using UV light but prevents or reduces transmission of UV light through the lens.